Insect World Digest
There are thousands of species of sweat bees in the cosmopolitan family Halictidae. They are small-to medium-sized bees and, in many habitats, are seen more than any other bees except the honeybee, Apis mellifera L., which is a large bee.
Barrows, Edward M., "Sweat Bees" (1976). Ba. Paper 72.
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